The path from a 2D image recorded in each of the HERMES arms to a
one-dimensional, continuum-normalized and zero-RV-shifted spectrum starts with
the following steps: raw image cosmetic corrections, spectral tracing,
optical aberrations correction, scattered light and apertures cross-talk
removal, wavelength calibration, sky subtraction, and telluric absorption
removal. Afterwards, spectra are continuum-normalized and shifted into
their rest-frame by cross-correlating them with a set of 15 AMBRE model
spectra [1]}. This procedure also yields initial
radial velocities, while initial stellar parameters (\(T_{\rm eff}\) , \(\log g\) , \(\mathrm {[Fe/H]}\) ) are determined by a (larger) grid of \(16\,783\)  AMBRE
spectra. These, internally also called GUESS parameters, were reported in
the first GALAH data release [2]}. The
spectra are then directed to the analysis pipeline with the aim of
delivering precise and accurate stellar atmospheric parameters and
individual elemental abundances, which constitute the core of results
reported in subsequent GALAH data releases.
